Abstract: A multi-limbed manometer system adapted to detect and record the vertical displacement of different parts of a large structure, e.g., the pedestals and cylinders of a steam turbine installation. The datum level of the liquid in the system is adjusted by changing the pressure of a head of liquid connected to the system, for example, by raising and lowering a reservoir of the system or by moving a piston in a cylinder connected to the system. The floats comprise homogeneous structures having a multiplicity of small air-filled compartments, e.g. an epoxy resin containing air-filled hollow glass balls having a diameter of about 150 microns. A float in a reference limb provides a reference signal indicative of the actual liquid level which is compared with a signal indicative of the desired liquid level and a difference signal derived and used to raise and lower the reservoir or move the piston in the cylinder.